Environmental Science & Technology,
Journal Year:
2024,
Volume and Issue:
58(19), P. 8501 - 8509
Published: May 2, 2024
Iron/chromium
hydroxide
coprecipitation
controls
the
fate
and
transport
of
toxic
chromium
(Cr)
in
many
natural
engineered
systems.
Organic
coatings
on
soil
surfaces
are
ubiquitous;
however,
mechanistic
these
organic
over
Fe/Cr
poorly
understood.
Here,
was
conducted
model
humic
acid
(HA),
sodium
alginate
(SA),
bovine
serum
albumin
(BSA).
The
organics
bonded
with
SiO2
through
ligand
exchange
carboxyl
(–COOH),
adsorbed
amounts
pKa
values
–COOH
controlled
surface
charges
coatings.
films
also
had
different
complexation
capacities
ions
particles,
resulting
significant
differences
both
amount
(on
HA
>
SA(–COOH)
≫
BSA(–NH2))
composition
(Cr/Fe
molar
ratio:
BSA(–NH2)
SA(–COOH))
heterogeneous
precipitates.
Negatively
charged
attracted
more
Fe
oligomers
hydrolyzed
species
subsequently
promoted
precipitation
nanoparticles.
containing
–NH2
were
positively
at
acidic
pH
because
high
value
functional
group,
limiting
cation
adsorption
formation
coprecipitates.
Meanwhile,
higher
local
near
Cr(OH)3.
This
study
advances
fundamental
understanding
organics,
which
is
essential
for
successful
Cr
remediation
removal
settings,
as
well
synthesis
Cr-doped
iron
(oxy)hydroxides
material
applications.
Environmental Science Nano,
Journal Year:
2025,
Volume and Issue:
unknown
Published: Jan. 1, 2025
Cr-incorporation
decreased
the
particle
size
of
Fe
hydroxides
and
promoted
their
intermediate
formation,
thus
As/Cr
removal
was
increased
by
promoting
adsorption
catalytic
efficiency
hydroxides.
The
biogeochemistry
of
arsenic
in
soils
is
strongly
controlled
by
iron
oxides
and
soil
organic
matter
(SOM).
present
study
intends
to
elucidate
the
behavior
Fe-SOM-As
composites
formed
through
adsorption
or
coprecipitation
under
redox
conditions.
X-ray
diffraction
(XRD)
high
resolution
transmission
electron
microscopy
(HRTEM)
showed
that
crystalline
minerals
were
generated
during
Fe-HA-As
coprecipitation,
while
other
exhibited
an
amorphous
structure.
In
anoxic
environment,
iron-reducing
bacteria
reduced
Fe(III)
As(V)
Fe(II)
As(III),
respectively,
enhancing
mobility
arsenic.
presence
SOM
increased
concentrations
dissolved
As(III)
complexation.
Notably,
elevated
observed
HA-containing
group
due
weak
capacity
minerals,
which
released
into
solution
competed
with
for
electrons.
Under
oxic
conditions,
superoxide,
hydrogen
peroxide,
hydroxyl
radical
(•OH)
oxidation
SOM.
was
subsequently
oxidized
superoxide
•OH,
process
dominated
•OH.
Substantial
•OH
mainly
limited
groups
contributed
greater
adsorbed
As(III).
These
findings
contribute
substantially
understanding
mechanisms
coupled
transformation
fluctuating
The
groups
from
dissolved
organic
matter
(DOM)
enhance
cadmium
(Cd)
immobilization
on
Fe
oxyhydroxide,
while
it
is
difficult
to
evaluate
the
contributions
of
different
binding
configurations
and
strength
between
Cd
oxyhydroxides
because
DOM's
complex
composition
lack
in
situ
methods.
Here,
we
selected
small
molecules
with
representative
functional
investigate
molecular
mechanisms
goethite
using
batch
experiments,
solid
characterization,
theoretical
calculations,
single-molecule
force
spectroscopy
(SMFS)
combined
K-means
analysis.
These
increase
adsorption
goethite,
carboxyl
showing
most
substantial
enhancement
(increased
by
81.7%).
Solid-state
characterization
reveals
that
primary
driver
enhanced
immobilization,
promoting
formation
new
Cd–O(C)
Cd–O(Fe/C)
bonds.
Especially,
thermodynamic
analysis
indicates
bonds
represent
75%–80%
total
presence
molecules.
Notably,
newly
developed
results
show
a
strong
correlation
capacity,
which
may
deepen
understanding
DOM-mediated
oxyhydroxides,
offering
crucial
insights
into
behavior
providing
basis
for
pollution
control
subsurface
superficial
environments.
